Update raw Ignition examples to use Ignition spec v3.4.0

* Regenerate example Ignition using fcct v0.18.0 to produce Ignition
spec v3.4.0 as a followup to https://github.com/poseidon/matchbox/pull/1079
* Fix one profile example where a double escape isn't needed

examples/ignition/fedora-coreos.ign

@@ -1,6 +1,6 @@
 {
   "ignition": {
-    "version": "3.3.0"
+    "version": "3.4.0"
   },
   "passwd": {
     "users": [

examples/ignition/flatcar-install.ign

@@ -1,6 +1,6 @@
 {
   "ignition": {
-    "version": "3.3.0"
+    "version": "3.4.0"
   },
   "passwd": {
     "users": [

examples/ignition/flatcar.ign

@@ -1,6 +1,6 @@
 {
   "ignition": {
-    "version": "3.3.0"
+    "version": "3.4.0"
   },
   "passwd": {
     "users": [

examples/profiles/fedora-coreos-install.json

@@ -10,7 +10,7 @@
       "initrd=main",
       "coreos.live.rootfs_url=http://matchbox.example.com:8080/assets/fedora-coreos/fedora-coreos-36.20220906.3.2-live-rootfs.x86_64.img",
       "coreos.inst.install_dev=/dev/vda",
-      "coreos.inst.ignition_url=http://matchbox.example.com:8080/ignition?uuid=$${uuid}&mac=$${mac:hexhyp}"
+      "coreos.inst.ignition_url=http://matchbox.example.com:8080/ignition?uuid=${uuid}&mac=${mac:hexhyp}"
     ]
   },
   "ignition_id": "fedora-coreos.ign"